We appreciate the interest in our findings about HIV-related racial disparities among MSM  from Schneider et al.. However, we wish to address some issues raised in their correspondence. First, Schneider et al. discuss appropriate analysis of data collected using venue-based, time-space sampling (VBS). To clarify, National HIV Behavioral Surveillance System (NHBS) procedures ensured that repeat participants were ineligible; therefore, the participant is an appropriate unit of analysis. Additionally, as we indicated, we explored accounting for clustering at the venue level and found only trivial differences between our models and models with venue-specific random effects.
Schneider et al. suggest that weighting VBS data for differences in venue attendance frequency is required. However, appropriate circumstances for weighting VBS data have yet to be determined. Indeed, recent publications in this and other journals have not weighted VBS data [3–9]. Nonetheless, Centers for Disease Control and Prevention (CDC) is currently determining appropriate circumstances and schemes for weighting future NHBS-MSM data.
Although CDC may determine that weighting is appropriate for some purposes, complex weighting is not required for all analyses. We were interested in the relationship between individual characteristics of the men surveyed and HIV infection; unweighted analysis was appropriate to answer these questions. Moreover, analysis of our data shows that although significantly more black than white MSM reported attending venues frequently, the HIV status of respondents and their most recent partners was not associated with venue attendance frequency. Furthermore, including venue attendance frequency as a covariate in our multivariable models produced only minor changes in estimates, supporting our contention that the differences we identified in these variables were not an artifact of VBS.
Schneider et al. raise a valid point about not generalizing from dyadic subnetwork analyses. Our publication was not a formal network analysis and we did not imply as much in our article, nor did we attempt to generalize to larger networks. However, our data about most recent male partners still warrant analysis, particularly because NHBS is larger and more geographically diverse than is practical for most network analyses. Although we examined ‘partnership characteristics’ rather than networks, these partnerships are rooted in networks and are associated with greater prevalence among black vs. other MSM [10,11]. Additionally, although black and white MSM differed with respect to characteristics such as age and socioeconomic status, we controlled for these factors in our logistic regression analysis.
Ultimately, although our analysis provides insight into a number of questions, a formal network analysis would undoubtedly allow exploration of more detailed questions about network structure and mixing, including serosorting. Although we did not aim to study serosorting, other studies have examined serosorting among MSM by race/ethnicity and found that black MSM are less likely than other MSM to serosort [12,13] and that serosorting provides a protective benefit for HIV-negative black MSM who serosort vs. those who do not . More importantly, HIV-negative black MSM who engage in serosorting are still more likely to test positive for HIV compared to MSM of other races who engage in serosorting [13,14]. Although Schneider's network-level data showing high levels of assortative mixing by serostatus among black MSM in Chicago are intriguing, they do not analyze differences in assortative mixing among black MSM compared with white MSM. Such an analysis may reinforce previous reports that show lower serosorting efficacy among black than white MSM.
Finally, we wish to clarify what appears to be an inaccurate characterization of our findings. We did not find that having a most recent partner of unknown HIV status resulted in an association with HIV infection that was more common among blacks. Rather, although we found an association between HIV infection and having a most recent partner of unknown HIV status, there was no statistically significant interaction to suggest that this association differed for black vs. white MSM. We did find, however, that more black than white MSM reported that their most recent partner was of unknown HIV status.
Although we feel that our analyses were appropriate for our data and questions, we agree with Schneider et al.  that black/white differences in sexual networks are important. In fact, our data suggest that factors other than individual risk behavior, including network factors and antiretroviral use, may contribute to HIV-related disparities among black and white MSM. Given the enormity of the HIV epidemic among MSM, particularly black MSM, it is critical that we respond promptly with surveillance, research, interventions, and prevention to change the course of this epidemic.
Conflicts of interest
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. There are no conflicts of interest.
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